Question 1

Which of the following best describes how a catalyst affects a chemical reaction?

Accepted Answer

It increases the rate of the reaction by lowering the activation energy without being consumed in the process.

Question 2

Which enzyme class is responsible for transferring a phosphate group from ATP to glucose in the first step of glycolysis?

Accepted Answer

Transferases

Question 3

A patient is exposed to diisopropyl fluorophosphate (DFP), which binds covalently to the active site serine of acetylcholinesterase. What type of enzyme inhibition is this?

Accepted Answer

Irreversible inhibition

Question 4

Which of the following statements about the induced fit model of enzyme-substrate interaction is correct?

Accepted Answer

The enzyme undergoes a conformational change upon substrate binding, optimizing the interaction.

Question 5

Which of the following mechanisms is NOT a way enzymes achieve rate acceleration?

Accepted Answer

Increasing the activation energy of the transition state

Question 6

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Increasing the apparent $$K_m$$ without affecting $$V_{max}$$

Question 7

Which of the following best describes the role of metal ions such as Zn$$^{2+} in $$enzyme catalysis?

Accepted Answer

They help bind substrates or stabilize negative charges during catalysis.

Question 8

Which of the following is an example of feedback inhibition in metabolic pathways?

Accepted Answer

The end product of a pathway inhibits an enzyme that acts early in the pathway.

Question 9

Which statement about allosteric enzymes is TRUE?

Accepted Answer

They are usually multisubunit proteins that change conformation upon effector binding.

Question 10

Which of the following is a correct description of a ribozyme?

Accepted Answer

An RNA molecule that catalyzes chemical reactions

Question 11

Which of the following is an example of reversible covalent modification regulating enzyme activity?

Accepted Answer

Phosphorylation by kinases and dephosphorylation by phosphatases

Question 12

A scientist discovers a molecule that binds only to the ES complex and not to the free enzyme. What type of inhibition is this?

Accepted Answer

Uncompetitive inhibition

Question 13

Which of the following statements about coenzymes is correct?

Accepted Answer

They are small organic molecules required for enzyme activity and are not irreversibly changed during catalysis.

Question 14

Which of the following is a characteristic of noncompetitive (mixed) inhibition?

Accepted Answer

The inhibitor can bind to both the free enzyme and the ES complex at a site distinct from the active site.

Question 15

Which of the following best explains why substrate-level control is considered a crude means of enzyme regulation?

Accepted Answer

A large change in substrate concentration $$[S] is $$required to significantly affect enzyme activity.

Question 16

Which of the following is an example of an irreversible covalent modification that activates an enzyme?

Accepted Answer

Proteolytic cleavage of a zymogen

Question 17

Which of the following is NOT a function of essential metal ions in enzymes?

Accepted Answer

Acting as a permanent part of the enzyme's primary structure

Question 18

Which of the following statements about enzyme inhibition is TRUE?

Accepted Answer

Reversible inhibitors bind noncovalently, while irreversible inhibitors bind covalently to the enzyme.

Question 19

Which of the following is a real-world example of enzyme regulation by covalent modification?

Accepted Answer

Activation of blood clotting factors by proteolytic cleavage

Question 20

Which of the following best describes the 'RNA World' hypothesis?

Accepted Answer

Ancient cells used RNA for both genetic information storage and catalysis before the evolution of DNA and proteins.

Enzymes: Biological Catalysts – Principles, Mechanisms, and Regulation

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